Method and system for creating an image of a radiation source

ABSTRACT

A method of creating an image of a radiation source includes detecting radiation associated with a first location of the radiation source. Data substantially corresponding to the radiation associated with the first location is processed to provide a first value. The first value is employed to generate a first portion of the image associated with the first location. Radiation associated with a second location of the radiation source is detected. Data substantially corresponding to the radiation associated with second location is processed to provide a second value. The second value is employed to generate a second portion of the image associated with the second location.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/802,465, filed Mar. 17, 2004, which is related to U.S. ProvisionalPatent Application Ser. No. 60/455,270, filed Mar. 17, 2003, the subjectmatter of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to creating an image of a radiationsource, and more specifically, to a method and a system for creating animage of a radiation source.

BACKGROUND OF THE INVENTION

In medical imaging, such as in Nuclear Medicine, a radioactive material,such as a radioactive tracer, is introduced into an object or a body toview parts of the object or body. The parts of the body that receive theradioactive material act as a radiation source for emitting radiation. Asystem for creating an image of the radiation source includes a detectorfor detecting radiation associated with the radiation source. Thedetector may be a gamma camera, a positron emission tomography (PET)camera, a solid state detector, or an x-ray detector. The spatialresolution and contrast of the image generated by the system is limitedby the intrinsic resolution or point spread function of the detector.

SUMMARY OF THE INVENTION

A method of creating an image of a radiation source includes detectingradiation associated with a first location of the radiation source. Datacorresponding to the radiation associated with the first location isprocessed to provide a first value. The first value is employed togenerate a first portion of the image associated with the firstlocation. Radiation associated with a second location of the radiationsource is detected. Data corresponding to the radiation associated withthe second location is processed to provide a second value. The secondvalue is employed to generate a second portion of the image associatedwith the second location.

In accordance with one feature, a system for creating the image of theradiation source includes an aggregator for aggregating the datacorresponding to radiation associated with the first location of theradiation source to provide the first value. The aggregator aggregatesthe data corresponding to radiation associated with the second locationof the radiation source to provide the second value. A mapping systemmaps the first value to a first portion of the image associated with thefirst location and maps the second value to a second portion of theimage associated with the second location.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomeapparent to those skilled in the art to which the present inventionrelates upon reading the following description with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic view of a portion of a system for creating animage of a radiation source;

FIG. 2 is a schematic view of the system of FIG. 1;

FIG. 3 is a plan view of a first embodiment of a plate member for use inthe system of FIG. 2;

FIG. 4 is a plan view of a second embodiment of a plate member for usein the system in FIG. 2;

FIG. 5 is a plan view of a third embodiment of a plate member for use inthe system in FIG. 2; and

FIG. 6 is a plan view of a portion of a fourth embodiment of a platemember for use in the system in FIG. 2.

DESCRIPTION OF THE INVENTION

The present invention is directed to a method and a system for creatingan image of a radiation source. A system for creating an image of aradiation source is illustrated in FIGS. 1-3. The system 10 (FIG. 1)includes a detector 12. The detector 12 detects radiation 14, such asionizing radiation, emitted from a radiation source 16. The system 10may be used in medical imaging to create an image of the radiationsource 16. The detector 12 may include a collimator, a crystal, photomultipliers, and/or solid state detector elements as known in the art.The detector 12 may be any suitable detector, such as a gamma camera, apositron emission tomography (PET) camera, a solid state detector, or anx-ray detector.

A plate member 22 is located between the detector 12 and the radiationsource 16. The plate member 22 is made of a suitable radiation absorbingmaterial, such as lead, and includes a plurality of apertures 24. It iscontemplated that the plate member 22 may have any desired thickness. Itis also contemplated that the plate member 22 may be used as acollimator for the detector 12. The radiation 14 from the radiationsource 16 only passes through the apertures 24 in the plate member 22 tothe detector 12. Accordingly, the detector 12 only detects radiation 28that passes through the apertures 24.

The apertures 24 (FIG. 3) are arranged in the plate member 22 in apredetermined pattern. The apertures 24 are arranged in a series of rowsand columns. The plate member 22 may have any desired number of rows andcolumns of apertures 24. Furthermore, the apertures 24 may be arrangedin any desired pattern. It is also contemplated that the plate member 22may have any desired number of apertures 24.

The apertures 24 (FIG. 3) are identical to each other. Each of theapertures 24 is square shaped. Each of the apertures 24 in the platemember 22 has a first dimension d1 measured in an x direction. Each ofthe apertures 24 has a second dimension d2 measured in a y direction.The first dimension d1 is equal to the second dimension d2. Thedimensions d1 and d2 are smaller than the intrinsic resolution or pointspread function of the detector 12. It is contemplated that theapertures 24 may have any desired shape, such as circular, triangular,rectangular or hexagonal. Furthermore, the apertures 24 may not beidentical to each other, may vary in size and shape and be arranged inconfigurations other than a rectangular pattern, if desired.

The apertures 24 are spaced from each other in the x direction by septaof a distance s1. The apertures 24 are spaced from each other in the ydirection by septa of a distance s2. The distance s1 is equal to thedistance s2. It is contemplated that the distance s1 may not be equal tothe distance s2. Each of the distances s1 and s2 is equal to two timesthe dimension d1. Accordingly, each of the distances s1 and s2 is equalto two times the dimension d2. Each of the distances s1 and s2 is largerthan the intrinsic resolution of the detector 12. Accordingly, each ofthe apertures 24 has a guard band surrounding the aperture. It iscontemplated that the distance s1 may be equal to any integer times thedimension d1 and that the distance s2 may be equal to any integer timesthe dimension d2.

Each of the apertures 24 (FIG. 1) is associated with a location of theradiation source 16. The locations of the radiation source 16 have sizesequal to the sizes of the apertures 24. Radiation 28 associated witheach of the locations of the radiation source 16 passes through theapertures 24 to the detector 12 while the plate member 22 preventspassage of radiation from the radiation source 16 at locations notassociated with the apertures. The detector 12 detects or samples theradiation 28 associated with each of the locations of the radiationsource 16. Accordingly, the detector 12 detects radiation 28 associatedwith a first location of the radiation source 16 that passes through afirst aperture 24 in the plate member 22. The detector 12 also detectsradiation 28 associated with a second location of the radiation source16 that passes through a second aperture 24 that is spaced from thefirst aperture.

A positioning mechanism 36 is connected with the plate member 22 to movethe plate member in the x direction or a first linear direction relativeto the detector 12 and the radiation source 16. The positioningmechanism 36 also moves the plate member 22 in the y direction or asecond linear direction relative to the detector 12 and the radiationsource 16. The positioning mechanism 36 moves the plate member 22 in astepwise manner relative to the detector 12 and the radiation source 16.It is contemplated that the positioning mechanism 36 may move the platemember 22 in a continuous linear motion in the x direction and acontinuous linear motion in the y direction. The positioning mechanism36 may be any suitable positioning mechanism for moving the plate member22 relative to the detector 12 and the radiation source 16, such as anelectric motor or manually operable mechanism. It is contemplated thatany number of positioning mechanisms 36 may be used to move the platemember 22.

The positioning mechanism 36 moves the plate member 22 relative to thedetector 12 and the radiation source 16 so that the detector detectsradiation associated with every location of the radiation source 16. Thepositioning mechanism 36 moves the plate member 22 in the x direction insteps having a distance equal to the dimension d1. The positioningmechanism 36 moves the plate member 22 in the y direction in stepshaving a distance equal to the dimension d2. The positioning mechanism36 positions the plate member 22 in nine steps in the x and y directionsso that the detector 12 detects radiation from every location of theradiation source 16. It is contemplated that the positioning mechanism36 may move the plate member 22 any suitable number of steps relative tothe detector 12 and the radiation source 16. Furthermore, thepositioning mechanism 36 may move the plate member 22 in the x directionin steps having a distance equal to a fraction of the dimension d1 andin the y direction in steps having a distance equal to a fraction of thedimension d2. It is also contemplated that the positioning mechanism 36may rotate the plate member 22 relative to the detector 12 and theradiation source 16.

The detector 12 (FIG. 2) is operably connected with a computer 50. Thecomputer 50 receives image data 52 from the detector 12. An imagingapplication 54 processes the image data 52 corresponding to theradiation 28 associated with the locations of the radiation source 16 toprovide a plurality of image values. The imaging application 54 employsthe image values to generate portions of the image associated with thelocations of the radiation source 16.

The imaging application 54 includes an aggregator 56 for processing theimage data 52. The aggregator 56 aggregates the image data 52corresponding to the radiation associated with the locations of theradiation source 16 to provide the image values. A mapping system 58 ofthe imaging application 54 maps the image values to correspondingportions of the image.

The computer 50 is operably connected to a display 62 for displaying theimage. An apparatus 64 is operably connected to the computer 50 forinputting user input, such as the locations and sizes of the apertures24 in the plate member 22. Other devices 68 may also be operablyconnected to the computer 50, such as a printer, a computer network,and/or the internet. It is also contemplated that the positioningmechanism 36 may be operably connected to the computer 50. The computer50 may operate the positioning mechanism 36 to move the plate member 22relative to the detector 12 and the radiation source 16.

The system 10 (FIGS. 1 and 2) operates to create an image of theradiation source 16 by positioning the plate member 22 in a firstposition relative to the detector 12 and the radiation source 16. Thedetector 12 detects or samples radiation 28 from the radiation source 16passing through the apertures 24 in the plate member 22. The detector 12detects radiation 28 associated with a first set of locations of theradiation source 16. The radiation 28 that passes through the apertures24 in the plate member 22 is detected by the detector 12. The detector12 produces Gaussian-like distributions or events of image data 52. Thedistributions of image data 52 are generally spread over an area that isgreater than the area of the apertures 24. The distributions of data donot overlap since the apertures 24 are spaced apart with guard bands bydistances s1 and s2 that are larger than the intrinsic resolution orpoint spread function of the detector 12. It is contemplated that thedistances s1 and s2 may be chosen such that the distributions mayoverlap. Accordingly, the detector 12 detects radiation 28 associatedwith a first location of the radiation source 16 that passes through afirst one of the apertures 24. The detector 12 also detects radiation 28associated with a second location of the radiation source 16 that passesthrough a second one of the apertures 24.

The image data 52 associated with the first set of locations isprocessed by the imaging application 54. The image data 52 correspondingto the radiation 28 associated with the first set of locations of theradiation source 16 is processed by the aggregator 56 to provide a firstset of image values. Accordingly, the aggregator 56 aggregates the imagedata 52 corresponding to the radiation 28 associated with the firstlocation of the radiation source 16 to produce a first image value. Theaggregator 56 aggregates the image data 52 corresponding to theradiation 28 associated with the second location to produce a secondimage value. The aggregator 56 may sum up the values of each of thedistributions to provide each of the image values. Accordingly, thestatistical noise associated with each of the image values is minimal.If the distributions of image data 52 overlap, the imaging application54 may correct the image values using experimentally determined orestimated contributions from the adjacent distributions. A sample imageof the radiation source 16 may be generated.

After the detector 12 detects the radiation 28 associated with the firstset of locations of the radiation source 16 with the plate member 22 inthe first position, the positioning mechanism 36 moves the plate memberin the x direction a distance equal to the dimension d1 into a secondposition. The detector 12 detects radiation 28 from the radiation source16 passing through the apertures 24 in the plate member 22. The detector12 detects radiation 28 associated with a second set of locations of theradiation source 16. The radiation 28 that passes through the apertures24 in the plate member 22 is detected by the detector 12. The detector12 produces distributions of image data 52. Accordingly, the detector 12detects radiation associated with a third location of the radiationsource 16 that passes through the first one of the apertures 24. Thedetector 12 also detects radiation 28 associated with a fourth locationof the radiation source 16 that passes through the second one of theapertures 24.

The image data 52 associated with the second set of locations isprocessed by the imaging application 54. The image data 52 correspondingto the radiation 28 associated with the second set of locations of theradiation source 16 is processed by the aggregator 56 to provide asecond set of image values. Accordingly, the aggregator 56 aggregatesthe image data 52 corresponding to the radiation 28 associated with thethird location of the radiation source 16 to produce a third imagevalue. The aggregator 56 aggregates the image data 52 corresponding tothe radiation 28 associated with the fourth location to produce a fourthimage value. A second sample image of the radiation source 16 may begenerated.

After the detector 12 detects the radiation 28 associated with thesecond set of locations of the radiation source 16 with the plate member22 in the second position, the positioning mechanism 36 moves the platemember in the y direction a distance equal to the dimension d2 into athird position. The detector 12 detects radiation 28 from the radiationsource 16 passing through the apertures 24 in the plate member 22. Thedetector 12 detects radiation 28 associated with a third set oflocations of the radiation source 16. The radiation 28 that passesthrough the apertures 24 in the plate member 22 is detected by thedetector 12. The detector 12 produces distributions of image data 52.Accordingly, the detector 12 detects radiation associated with a fifthlocation of the radiation source 16 that passes through the first one ofthe apertures 24. The detector 12 also detects radiation 28 associatedwith a sixth location of the radiation source 16 that passes through thesecond one of the apertures 24.

The image data 52 associated with the third set of locations isprocessed by the imaging application 54. The image data 52 correspondingto the radiation 28 associated with the third set of locations of theradiation source 16 is processed by the aggregator 56 to provide a thirdset of image values. Accordingly, the aggregator 56 aggregates the imagedata 52 corresponding to the radiation 28 associated with the fifthlocation of the radiation source 16 to produce a fifth image value. Theaggregator 56 aggregates the image data 52 corresponding to theradiation 28 associated with the sixth location to produce a sixth imagevalue. A third sample image of the radiation source 16 may be generated.

The steps of moving the plate member 22, detecting radiation 28associated with a set of locations, and processing the image data 52associated with the set of locations is repeated until radiationassociated with every location of the radiation source 16 is detected.The steps need to be repeated at least nine times to detect radiation 28from every location of the radiation source 16. The number of steps thatare needed to detect radiation emitted from every location of theradiation source 16 is a function of the size of the apertures 24 in theplate member 22 and the distances s1 and s2 between the apertures. It iscontemplated that any number of steps could be used to detect radiationemitted from every location of the radiation source.

The mapping system 58 employs the image values to generate the image ofthe radiation source 16. The mapping system 58 maps the image values toportions or pixels of the image that correspond to the locations of theradiation source 16. Each of the portions of the image has an area thatis equal to the area of the aperture 24 in the plate member 22. Theimage values in each of the portions of the image do not contain dataassociated with any other locations of the radiation source 16.Accordingly, the spatial resolution of the system 10 is equal to thesize of the apertures 24 in the plate member 22 and is independent ofthe spatial resolution or point spread function of the detector 12.

The mapping system 58 maps the first image value to a first portion ofthe image that corresponds to the first location of the radiation source16. The first portion of the image has an area that is equal to the areaof the aperture 24 in the plate member 22. The image value in the firstportion of the image does not contain any data associated with any otherlocations of the radiation source 16. The mapping system 58 maps thesecond image value to a second portion of the image that corresponds tothe second location of the radiation source 16. The second portion ofthe image has an area that is equal to the area of the aperture 24 inthe plate member 22. The image value in the second portion of the imagedoes not contain any data associated with any other locations of theradiation source 16. The mapping system 58 maps all the image values tocorresponding portions of the image. Accordingly, the image has aresolution equal to the size of the apertures 24 in the plate member 22,which may be smaller than the intrinsic resolution of the detector 12.The image also has an improved contrast since each of the portions ofthe image does not include data associated with any other locations ofthe radiation source 16. It is contemplated that each of the portions ofthe image may include a minimal amount of data associated with anotherlocation of the radiation source 16. It is contemplated that if thedistributions of image data 52 overlap, the imaging application 54 maycorrect the image values using experimentally determined or estimatedcontributions from the adjacent distributions.

A plate member 122 constructed in accordance with a second embodimentfor use in the system shown in FIGS. 1-2 is illustrated in FIG. 4. Theplate member 122 shown in FIG. 4 is made of a suitable radiationabsorbing material, such as lead, and includes a plurality of apertures124. It is contemplated that the plate member 122 may have any desiredthickness. It is also contemplated that the plate member 122 may be usedas a collimator for the detector 12. The detector 12 only detectsradiation 28 that passes through the apertures 124.

The apertures 124 are arranged in the plate member 122 in apredetermined pattern. The apertures 124 are arranged in a series ofrows and columns. The plate member 122 may have any desired number ofrows and columns of apertures 124. Furthermore, the apertures 124 may bearranged in any desired pattern. It is also contemplated that the platemember 122 may have any desired number of apertures 124.

The apertures 124 are identical to each other. Each of the apertures 124is square shaped. Each of the apertures 124 in the plate member 122 hasa first dimension d3 measured in an x direction. Each of the apertures124 has a second dimension d4 measured in a y direction. The firstdimension d3 is equal to the second dimension d4. The dimensions d3 andd4 are smaller than the intrinsic resolution or point spread function ofthe detector 12. It is contemplated that the apertures 124 may have anydesired shape, such as circular, triangular, rectangular or hexagonal.Furthermore, the apertures 124 may not be identical to each other andmay vary in size and shape if desired.

The apertures 124 are spaced from each other in the x direction by septaof a distance s3. The apertures 124 are spaced from each other in the ydirection by septa of a distance s4. An aperture 124 in one row is notspaced in the y direction from the apertures in the adjacent rows.Adjacent columns are spaced from each other in the x direction by adistance s5 that is equal to the distance s4. The distance s3 is equalto eight times the dimension d3. The distance s4 is equal to two timesthe dimension d4. The distance s5 is equal to two times the dimensiond3. The distances s3, s4, and s5 are larger than the intrinsicresolution of the detector 12. Accordingly, each of the apertures 124has a guard band surrounding the aperture. It is contemplated that thedistance s3 may be equal to any integer times the dimension d3. It iscontemplated that the distance s4 may be equal to any integer times thedimension d4 and that the distance s5 may be equal to any integer timesthe dimension d3.

Each of the apertures 124 is associated with a location of the radiationsource 16. The locations of the radiation source 16 have sizes equal tothe sizes of the apertures 124. The radiation 28 associated with each ofthe locations of the radiation source 16 passes through the apertures124 to the detector 12 while the plate member 122 prevents passage ofradiation from the radiation source at locations not associated with theapertures. The detector 12 detects or samples the radiation 28associated with each of the locations of the radiation source 16.Accordingly, the detector 12 detects radiation 28 associated with afirst location of the radiation source 16 that passes through a firstaperture 124 in the plate member 122. The detector 12 also detectsradiation 28 associated with a second location of the radiation source16 that passes through a second aperture 124 that is spaced from thefirst aperture.

The positioning mechanism 36 is connected with the plate member 122 tomove the plate member in the x direction or a first linear directionrelative to the detector 12 and the radiation source 16. The positioningmechanism 36 moves the plate member 122 in a stepwise manner relative tothe detector 12 and the radiation source 16. It is contemplated that thepositioning mechanism may move the plate member 122 in a continuouslinear motion in the x direction.

The positioning mechanism 36 moves the plate member 122 relative to thedetector 12 and the radiation source 16 so that the detector detectsradiation associated with every location of the radiation source 16. Thepositioning mechanism 36 moves the plate member 122 in the x directionin steps having a distance equal to the dimension d3. The positioningmechanism 36 positions the plate member 122 in nine steps in the xdirection so that the detector 12 detects radiation from every locationof the radiation source 16. It is contemplated that the positioningmechanism 36 may move the plate member 122 any suitable number of stepsrelative to the detector 12 and the radiation source 16. Furthermore,the positioning mechanism 36 may move the plate member 122 in stepshaving a distance equal to a fraction of the dimension d3. Accordingly,the positioning mechanism 36 only moves the plate member 122 in onelinear direction so that the detector 12 detects radiation 28 from everylocation of the radiation source 16.

A plate member 222 constructed in accordance with a third embodiment foruse in the system shown in FIGS. 1-2 is illustrated in FIG. 5. The platemember 222 shown in FIG. 5 is made of a suitable radiation absorbingmaterial, such as lead, and includes a plurality of apertures 224. It iscontemplated that the plate member 222 may have any desired thickness.It is also contemplated that the plate member 222 may be used as acollimator for the detector 12. The detector 12 only detects radiation28 that passes through the apertures 224. The apertures 224 are arrangedin the plate member 222 in a predetermined pattern. The apertures 224are arranged in a honeycomb pattern. The apertures 224 may be arrangedin any desired pattern. It is contemplated that the plate member 222 mayhave any desired number of apertures 224.

The apertures 224 are identical to each other. Each of the apertures 224is hexagonal shaped. Each of the apertures 224 has a size smaller thanthe intrinsic resolution of the detector 12. The apertures 224 arespaced from each other so that each aperture has a hexagonal space 226equal in size to the aperture to each side of the aperture that does notoverlap a hexagonal space to a side of another aperture. The distancesbetween the apertures 224 are larger than the intrinsic resolution ofthe detector 12. Accordingly, each of the apertures 224 has a guard bandsurrounding the aperture. It is contemplated that the apertures 224 mayhave any desired shape, such as circular, triangular, rectangular orsquare shaped. Furthermore, the apertures 224 may not be identical toeach other and may vary in size and shape if desired.

Each of the apertures 224 is associated with a location of the radiationsource 16. The locations of the radiation source 16 have sizes equal tothe sizes of the apertures 224. The radiation 28 associated with each ofthe locations of the radiation source 16 passes through the apertures224 to the detector 12 while the plate member 222 prevents passage ofradiation from the radiation source at locations not associated with theapertures. The detector 12 detects or samples the radiation 28associated with each of the locations of the radiation source 16.Accordingly, the detector 12 detects radiation 28 associated with afirst location of the radiation source 16 that passes through a firstaperture 224 in the plate member 222. The detector 12 also detectsradiation 28 associated with a second location of the radiation source16 that passes through a second aperture 224 that is spaced from thefirst aperture.

The positioning mechanism 36 is connected with the plate member 222 tomove the plate member relative to the detector 12 and the radiationsource 16. The positioning mechanism 36 moves the plate member 222 in astepwise manner relative to the detector 12 and the radiation source 16.It is contemplated that the positioning mechanism 36 may move the platemember 222 in a continuous motion.

The positioning mechanism 36 moves the plate member 222 relative to thedetector 12 and the radiation source 16 so that the detector detectsradiation associated with every location of the radiation source 16. Thepositioning mechanism 36 moves the plate member 222 in steps having adistance equal to the size of the apertures 224. The positioningmechanism 36 positions the plate member 222 in at least seven steps sothat the detector 12 detects radiation from every location of theradiation source 16. It is contemplated that the positioning mechanism36 may move the plate member 222 any suitable number of steps relativeto the detector 12 and the radiation source 16. Furthermore, thepositioning mechanism 36 may move the plate member 222 in steps having adistance equal to a fraction of the size of the apertures 224. Thepositioning mechanism 36 may move the plate member 222 in one lineardirection extending perpendicular to sides of the apertures 224 so thatthe detector 12 detects radiation from every location of the radiationsource 16. The positioning mechanism 36 may move the plate member 222 ina circular pattern so that the detector 12 detects radiation from everylocation of the radiation source 16.

A portion of a plate member 322 constructed in accordance with a fourthembodiment for use in the system shown in FIGS. 1-2 is illustrated inFIG. 6. The plate member 322 shown in FIG. 6 is made of a suitableradiation absorbing material, such as lead, and includes a plurality ofapertures 324. It is contemplated that the plate member 322 may have anydesired thickness. It is also contemplated that the plate member 322 maybe used as a collimator for the detector 12. The detector 12 onlydetects radiation 28 that passes through the apertures 324.

The apertures 324 are arranged in the plate member 322 in apredetermined pattern. The apertures 324 are arranged in a series ofrows and columns. The plate member 322 may have any desired number ofrows and columns of apertures 324. Furthermore, the apertures 324 may bearranged in any desired pattern. It is also contemplated that the platemember 322 may have any desired number of apertures 324.

The apertures 324 are identical to each other. Each of the apertures 324is square shaped. Each of the apertures 324 in the plate member 322 hasa first dimension d5 measured in an x direction. Each of the apertures324 has a second dimension d6 measured in a y direction. The firstdimension d5 is equal to the second dimension d6. The dimensions d5 andd6 are smaller than the intrinsic resolution or point spread function ofthe detector 12. It is contemplated that the apertures 324 may have anydesired shape, such as circular, triangular, rectangular or hexagonal.Furthermore, the apertures 324 may not be identical to each other andmay vary in size and shape if desired.

The apertures 324 are spaced from each other in the x direction by septaof a distance s6. The apertures 324 are spaced from each other in the ydirection by septa of a distance s7. The distances s6 and s7 are equalto each other and the dimensions d5 and d6. Accordingly, each of theapertures 324 has a guard band surrounding the aperture.

Each of the apertures 324 is associated with a location of the radiationsource 16. The locations of the radiation source 16 have sizes equal tothe sizes of the apertures 324. The radiation 28 associated with each ofthe locations of the radiation source 16 passes through the apertures324 to the detector 12 while the plate member 322 prevents passage ofradiation from the radiation source at locations not associated with theapertures. The detector 12 detects or samples the radiation 28associated with each of the locations of the radiation source 16.Accordingly, the detector 12 detects radiation 28 associated with afirst location of the radiation source 16 that passes through a firstaperture 324 in the plate member 322. The detector 12 also detectsradiation 28 associated with a second location of the radiation source16 that passes through a second aperture 324 that is spaced from thefirst aperture.

The positioning mechanism 36 is connected with the plate member 322 tomove the plate member in the x direction or a first linear directionrelative to the detector 12 and the radiation source 16. The positioningmechanism 36 also moves the plate member 322 in the y direction relativeto the detector 12 and the radiation source 16. The positioningmechanism 36 moves the plate member 322 in a stepwise manner relative tothe detector 12 and the radiation source 16. It is contemplated that thepositioning mechanism 36 may move the plate member 322 in a continuousmotion.

The positioning mechanism 36 moves the plate member 322 relative to thedetector 12 and the radiation source 16 so that the detector detectsradiation associated with every location of the radiation source 16. Thepositioning mechanism 36 moves the plate member 322 in the x directionin steps having a distance equal to the dimension d5. The positioningmechanism 36 moves the plate member 322 in the y direction in stepshaving a distance equal to the dimension d6. The positioning mechanism36 positions the plate member 322 in four steps in the x and ydirections so that the detector 12 detects radiation from every locationof the radiation source 16. It is contemplated that the positioningmechanism 36 may move the plate member 322 any suitable number of stepsrelative to the detector 12 and the radiation source 16. Furthermore,the positioning mechanism 36 may move the plate member 322 in the xdirection in steps having a distance equal to a fraction of thedimension d5 and in the y direction in steps having a distance equal toa fraction of the dimension d6.

The plate member 322 is ideally suited for use with a solid statedetector, such as a cadmium zinc telluride detector. The solid statedetector has an array of detector elements that are generally square incross-section. The apertures 324 in the plate 322 have a size equal toone quarter the size of the detector elements. It is contemplated thatthe apertures 324 may be any desired fractional size of the detectorelements. The apertures 324 are positioned to expose only one quadrantof the detector elements at a time. The plate member 322 is subsequentlypositioned to expose different quadrants of the detector elements untilthe detector detects radiation from every location of the radiationsource 16.

The size of the apertures 24,124, 224, and 324 in the plate members22,122, 222, and 322 determine the spatial resolution of the system 10.The smaller the apertures 24, 124, 224, and 324 the better the spatialresolution. Accordingly, the spatial resolution or point spread functionof the detector 12 does not determine the spatial resolution of thesystem 10. The distances between the apertures 24, 124, 224, and 324determine the contrast of the system 10. The larger the distancesbetween the apertures 24, 124, 224, and 324 the better the contrast. Ifthe apertures 24, 124, 224, and 324 are relatively small and thedistances between the apertures are relatively large, a greater numberof steps are needed to detect radiation 28 from every location of theradiation source 16.

Each image value provided by the aggregator 56 of the system 10 has astatistical noise. The statistical noise associated with each imagevalue is defined as the inverse of the square root of the image value.The image values provided by the aggregator 56 are generated by summingthe values of each of the distributions. Therefore, the image valuesprovided by the aggregator 56 are larger than or equal to image valuesobtained by not summing the values of the distributions. Accordingly,the image generated by using the image values provided by the aggregator56 of the system 10 has less statistical noise.

Although the plate members 22, 122, 222, and 322 are described as beinglocated between the radiation source 16 and the detector 12, it iscontemplated that the plate members may be used instead of thecollimator of the detector.

Although the positioning mechanism 36 moves the plate members 22,122,222, and 322 relative to the radiation source 16 and the detector 12 sothat the detector detects radiation 28 associated with every location ofthe radiation source, it is contemplated that the positioning mechanismmay move the plate members such that the detector does not detectradiation associated with every location of the radiation source. Theimaging application 54 may estimate the image values that correspond tothe locations of the radiation source 16 that are not detected. Themapping system 58 may map the estimated image values to correspondingportions of the image.

It is contemplated that the plate members 22, 122, 222, and 322 may befixed to the detector 12, such as a rotating SPECT (single photonemission computer tomography) camera. A positioning mechanism may rotatethe detector 12 and the plate member fixed to the detector relative tothe radiation source 16 about an axis extending parallel to the platemember. The detector 12 and the plate member fixed to the detector maybe rotated in a continuous or stepwise manner around the radiationsource 16. The rotation of the detector 12 and the plate member fixed tothe detector permits the detection of radiation 28 from every locationof the radiation source 16 from multiple angles around the axis ofrotation of the detector. The computer 50, using various mathematicaltechniques, may construct transaxial cross sections through theradiation source 16.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes and modifications within the skill of the art areintended to be covered by the appended claims.

1. A method of creating an image of a radiation source comprising:detecting radiation associated with a first location of the radiationsource; processing only data substantially corresponding to theradiation associated with the first location to provide a first value;employing the first value to generate a first portion of the imageassociated with the first location; detecting radiation associated witha second location of the radiation source; processing only datasubstantially corresponding to the radiation associated with the secondlocation to provide a second value; and employing the second value togenerate a second portion of the image associated with the secondlocation.
 2. A method as set forth in claim 1 further includingdetecting radiation associated with a first location of the radiationsource, the first location having a size that is smaller than theresolution of a detector used for detecting the radiation and detectingradiation associated with a second location of the radiation source, thesecond location having a size that is smaller than the resolution of thedetector.
 3. A method as set forth in claim 1 further includingproviding a member for preventing radiation of the radiation source frombeing detected between the radiation source and a detector for detectingradiation, the member having an aperture through which radiationassociated with the first and second locations passes.
 4. A method asset forth in claim 3 further including detecting radiation associatedwith a first location located substantially adjacent to a secondlocation while preventing detection of radiation associated with thesecond location and detecting radiation associated with the secondlocation while preventing detection of radiation associated with thefirst location.
 5. A method as set forth in claim 3 further includingplacing the member in a first position relative to the detector whiledetecting radiation associated with the first location and placing themember in a second position relative to the detector while detectingradiation associated with the second location.
 6. A method as set forthin claim 5 further including moving the member and the detector relativeto each other in only one linear direction from the first position tothe second position.
 7. A method as set forth in claim 3 furtherincluding providing the aperture in the member with a size smaller thanthe resolution of the detector.
 8. A method as set forth in claim 1further including providing a member for preventing radiation associatedwith a third location of the radiation source from being detectedbetween the radiation source and a detector for detecting radiation, themember having first and second apertures spaced from each other throughwhich radiation associated with the first and second locations passes.9. A method as set forth in claim 8 further including simultaneouslydetecting radiation associated with the first and second locations. 10.A method as set forth in claim 1 further including summing values of adistribution of data substantially corresponding to the radiationassociated with the first location to provide the first value.
 11. Amethod as set forth in claim 10 further including summing values of adistribution of data substantially corresponding to the radiationassociated with the second location to provide the second value.
 12. Asystem for creating an image of a radiation source comprising: anaggregator for aggregating only data substantially corresponding toradiation associated with a first location of the radiation source toprovide a first value, said aggregator aggregating only datasubstantially corresponding to radiation associated with a secondlocation of the radiation source to provide a second value; and amapping system for mapping the first value to a first portion of theimage associated with the first location and for mapping the secondvalue to a second portion of the image associated with the secondlocation.
 13. A system as set forth in claim 12 further including adetector for detecting the radiation associated with the first andsecond locations.
 14. A system as set forth in claim 13 furtherincluding a member for preventing radiation of the radiation source frombeing detected between the radiation source and the detector, saidmember having an aperture through which radiation associated with thefirst and second locations passes.
 15. A system as set forth in claim 14wherein said aperture has a size smaller than the resolution of thedetector.
 16. A system as set forth in claim 14 further including meansfor moving the member and the detector relative to each other.
 17. Asystem as set forth in claim 13 further including a member forpreventing radiation associated with a third location of the radiationsource from being detected between the radiation source and thedetector, said member having first and second apertures spaced from eachother through which radiation associated with the first and secondlocations passes.
 18. A system as set forth in claim 17 wherein each ofsaid first and second apertures has a size smaller than the resolutionof the detector.
 19. A system as set forth in claim 17 further includingmeans for moving the member and the detector relative to each other.